Erythroblastic leukemic (EBL) cells are chemically induced tumor cells which have been used as models of normal erythroblasts. We have demonstrated that exposure of EBL cells to high amino acid concentrations results in subsequent increased insulin binding. This proposal is concerned with extending these preliminary observations in EBL cells to elucidate whether the effects of amino acids are mediated by changes in receptor number or affinity, which amino acids are responsible and the mechanisms of action. Additionally, we propose to examine the mechanisms of insulin-induced down-regulation and the interaction of both insulin and amino acids concurrently. Both biochemical (competitive insulin binding assays) and morphological (electron microscope radioautography) techniques will be combined to achieve these ends. We also plan to seek these effects in normal cells using the cultured human fibroblast and the isolated rat hepatocyte. If normal cells also exhibit increased insulin binding with amino acids we believe the observation may have important physiological implications in control of insulin receptor homeostasis and hence, insulin responsiveness. As such, elucidation of the mechanisms involved may be expected to furhter our understanding of insulin regulated phenomena and pathologies such as diabetes mellitus and related disorders, and thence help rationalize available therapies.